This invention relates to circuits, for example, a start circuit for a self-oscillating power supply control integrated circuit.
One application for a self-oscillating power supply control circuit is in a boost converter application wherein an input AC signal is converted to an output DC voltage. Further, it is well known that to initiate the operation of the power supply control integrated circuit (IC), a start circuit is required.
Most, if not all, self-oscillating start circuits for power supply control integrated circuits are external and utilize an external free running oscillator signal that is summed with a current detect signal at one input of the power supply control integrated circuit to initiate power supply operation. However, this approach requires that an input to the current detect comparator of the power supply control integrated circuit must be properly weighted such that the start signal from the external oscillator does not interfere with normal operation. These start circuits are only utilized to initiate the power supply operation and do not monitor the output off time of the power supply upon initiation. Further, external oscillators require additional components which increase the cost of the power supply.
Hence, there exists a need to provide an improved start circuit for a power supply control integrated circuit that monitors the output off time of the power supply, while not requiring additional external components.